A number of polymeric materials having useful therapeutic activity have been described for treatment of various conditions such as hyperlipidemia and hyperphosphatemia. Many of these polymeric materials function as non-absorbed ion exchange resins in the digestive tract. Such non-absorbed polymeric materials bind or otherwise sequester a target molecule and facilitate its removal from the body via the gastrointestinal tract. Examples of such resins include: Colestipol and Cholestyramine useful as orally administered cholesterol lowering agents; a variety of aliphatic amine polymers disclosed U.S. Pat. Nos. 5,496,545 and 5,667,775 useful as phosphate binders particularly for removing phosphate from patients suffering from renal failure; and other aliphatic amine polymers disclosed in U.S. Pat. No. 5,624,963, U.S. Pat. No. 5,679,717, WO98/29107 and WO99/22721 useful as cholesterol lowering agents.
Non-absorbed polymer therapeutics have traditionally presented a number of formulation challenges as the dosages are generally very large (gram quantities), and the resins tend to be extremely hydrophilic. The most desirable formulation for oral delivery of a therapeutic is a direct compression tablet formulation. However, not all therapeutics, particularly given the high dose requirements of polymeric ion exchange therapeutics, lend themselves to a tablet formulation. Even if such materials could be rendered into a tablet, it is generally not possible without the significant addition of other materials which assist in the tableting process. Ultimately the addition of any materials other than the active ingredient is undesirable given the dose requirement of the active ingredient. Ideally the tablet should contain as much active ingredient as possible with little else in the way of additional materials such that the tablet is as small as possible and easy to administer to the patient.
In addition, once the polymeric materials are compressed into a tablet, the tablet requires a coating for ease of administration to the patient. It has been discovered that the core polymeric material tends to be very hygroscopic, and thus will swell immediately upon contact with the inside of the mouth. Most coatings contain water, and thus it was believed that coating such tablets with a water-based coating would be impossible because the hygroscopic tablets would swell during the coating process. Thus providing a tablet core comprising a hygroscopic material such that a suitable coating may be used in conjunction with that core, is another significant challenge to providing the polymeric active ingredient in tablet form.
There is a need to provide suitable dosage forms for polymeric ion exchange materials, particularly for hydrophilic aliphatic amine polymers useful as therapeutic agents, which minimize the overall amount of material administered to the patient, which are easy to administer orally, and which are stable upon production and storage.
The present invention provides a tablet core which comprises at least about 95% by weight of an aliphatic amine polymer. In a preferred embodiment, the aliphatic amine polymer resin is a cross-linked polyallylamine resin. The aliphatic amine polymer is preferably hydrated. The hydrated polymer can, for example, comprise from about 5% water by weight or greater.
The invention also provides a method of producing a tablet core comprising at least about 95% by weight of an aliphatic amine polymer resin. The method comprises the step of compressing the aliphatic amine polymer to form the tablet core. The tablet core can further include one or more excipients. In this embodiment, the method of producing the tablet core comprises the steps of: (1) hydrating or drying the aliphatic amine polymer to the desired moisture level; (2) blending the aliphatic amine polymer with the excipients in amounts such that the polymer comprises at least about 95% by weight of the resulting blend; and (3) compressing the blend to form the tablet core. The present invention further relates to a coated tablet wherein the coating comprises a water based coating.